This specification relates to optical communication.
Wavelength Division Multiplexing (WDM) technology has been widely used in optical fiber communications to increase the transmission capacity for point to point data transmission through a single optical fiber. Various conventional WDM laser technologies have been developed. Solutions suitable for Dense WDM (DWDM) applications and with high speed modulation performance at 10 Gigabit/second or above are typically desired.
Conventional or proposed WDM laser solutions include fixed wavelength externally modulated laser (EML), wavelength tunable lasers, externally seeded injection locked Fabry-Perot (FP) lasers, and reflective optical amplifier (RSOA) lasers.
Other conventional architectures can include self-seeding mechanisms in which drop fibers connecting the light sources to the passive distribution node serve as part of the laser cavity, and a partial reflector on the transmission side of the WDM multiplexer (MUX) at the passive node together with the WDM MUX serves as the wavelength selective mirror in the laser cavity to lock the laser wavelength to the channel defined by the WDM MUX. Though such architectures greatly simplify a passive optical network WDM (WDM-PON) system, it is nevertheless challenging to manage a long external cavity laser for stable and high performance transmission at high data rates and long distance.